I had a client with this request. This is how I did it but it would strongly recommend you strand test this process first to see how the hair stands up.
First I bleach bathed the whole head, 1 scoop of powder (I use Tigi as it seems to be the gentlest), I scoop of 6% peroxide, 1 scoop of warm water: you obviously keep doubling it to make a large batch but keep to those ratios.
Lift the hair to an orange base 6. This mix can stay on for 50 mins. If it doesn't lift enough, wash off, dry and repeat application.
On the dried hair, drench in porosity balancer and dry in until bone dry.
Full head of woven with Tigi tru light and 6%
Inbetween the packets, flood with Schwartzkopf perfect 10, 7/0 and 7/12 and 3%. This is a colour that needs a minimum of 10 mins to deposit. You can leave it one longer but it means if the foils process quickly you can take the whole lot after 10 mins.
Once rinsed off, I put Steel blue and 2% straight over (Schwartzkopf, blondeme) and develop visually. Then a deep conditioning treatment to close the cuticle.
This gives a nice ash blonde result. I always give a blue shampoo, to maintain the result, as aftercare.